CVE-2026-73570

Synacor Zimbra Collaboration Suite (ZCS): OS Command Injection

As of , CVE-2026-73570 in Synacor Zimbra Collaboration Suite (ZCS) is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch now.

Exploited
Yes: CISA listed it on 21 August 2026
US federal deadline
24 August 20263 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
Forensic triage
Required by CISA under BOD 26-04Agencies must also look for signs that attackers already got in.
EPSS score
0.72Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
Public exploit
None foundNeither Metasploit nor Exploit-DB lists one.
Fix
Vendor advice: blog.zimbra.com and wiki.zimbra.comLinks below, from CISA's entry.

What CISA says to do

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

CISA's required action

What the flaw is

Zimbra Collaboration Suite (ZCS) contains an OS command injection vulnerability which could allow an unauthenticated attacker to send specially crafted SMTP requests that may result in execution of arbitrary operating system commands as the Zimbra user.

CISA's description

A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zimbra-snmp package is installed and SNMP notifications are enabled. Due to improper sanitization of untrusted input during SNMP notification processing, an unauthenticated attacker can send specially crafted SMTP requests that may result in execution of arbitrary operating system commands as the Zimbra user.

The CVE record's description, from mitre

CVE published
13 August 2026
Assigned by
mitre
CVSS
8.9 High (CVSS 3.1, from the CNA)
CWE-78
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
CISA SSVC, exploitation
active
CISA SSVC, automatable
no
CISA SSVC, technical impact
total

EPSS since listing

0.250.500.750.50: the rank's Patch this week line0.12 on 5 October 20260.72 since 6 October 2026
EPSS for CVE-2026-73570 since our EPSS history begins, on the days its value to 2 decimals changed. EPSS scores by FIRST.
Show the numbers
FromEPSS
0.12
0.72

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Zimbra Collaboration Suite (ZCS): other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2019-9621Server-Side Request Forgery (SSRF)Synacor Zimbra Collaboration Suite (ZCS)Patch this weekMetasploit module; EPSS 0.81; verified Exploit-DB entry0.81
CVE-2019-9670Improper Restriction of XML External Entity ReferenceSynacor Zimbra Collaboration Suite (ZCS)Patch this weekMetasploit module; EPSS 0.99; verified Exploit-DB entry0.99
CVE-2022-41352Arbitrary File UploadSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; Metasploit module; EPSS 0.950.95
CVE-2022-27925Arbitrary File UploadSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; Metasploit module; EPSS 0.990.99
CVE-2022-37042Authentication BypassSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; Metasploit module; EPSS 0.920.92
CVE-2023-34192Cross-Site Scripting (XSS)Synacor Zimbra Collaboration Suite (ZCS)Patch this weekEPSS 0.770.77
CVE-2024-45519Command ExecutionSynacor Zimbra Collaboration Suite (ZCS)Patch this weekEPSS 0.990.99
CVE-2022-27924Command InjectionSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; EPSS 0.940.94
CVE-2018-6882Cross-Site Scripting (XSS)Synacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use0.30
CVE-2025-68645PHP Remote File InclusionSynacor Zimbra Collaboration Suite (ZCS)Patch soon0.49

All 17 entries for Zimbra Collaboration Suite (ZCS)

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